Field of the Invention
The present invention is generally directed toward methods of cleaning and descaling surfaces of equipment contaminated with food or beverage soils. In addition, the methods of the present invention generally result in a substantial reduction of bacteria and/or other microorganisms present on the surfaces of the equipment. More particularly, the methods according to the present invention comprise a single cycle cleaning method that can reduce water usage or entirely obviate the need for a pre-rinse step, and is especially suited for use with clean-in-place systems.
Description of the Prior Art
Clean-in-place (CIP) systems are commonly used in many food industries, including dairy, beverage, brewing, and processed foodstuffs. These systems are also commonly used in the pharmaceutical and cosmetics industries. These systems are designed such that the interior pipes, vessels, process equipment, and associated fittings can be cleaned without disassembly of the equipment. Adequate cleaning of food preparation surfaces is a necessity to ensure the safety of the food supplied to consumers. This is especially true for the dairy industry, food preparation and processing plants, including food and beverage plants, and particularly in the area of milk handling and storing. Fresh milk must be immediately cooled and refrigerated after being obtained from the cow in order to prevent the milk from spoiling. Consequently, the piping systems, equipment, storage tanks, and utensil surfaces which handle the flow of milk must be cleaned after each milking in order to remove milk soils so as to prevent contamination of the fresh milk supply during subsequent milking operations. Most dairies operate using at least two milkings per day. This means that the CIP systems must be cleaned at least twice per day.
Traditionally, CIP systems in North America (the United States and Canada) have always been cleaned using chlorinated alkaline or alkaline detergents and at least a three-step process. In the first step, the system is pre-rinsed with water at about 37-49° C. (100-120° F.). The goal in this step is to soften or melt the milk fats, without using water so hot as to denature the milk proteins and create scale. It has been conventionally thought that this step was a necessary prerequisite to the cleaning process and for scale inhibition. In the second step, the system is washed with hot water of no less than 49° C. (120° F.), and usually closer to about 70-80° C. (158-176° F.), using the chlorinated alkaline or alkaline detergent, which is circulated through the system for about 8-10 minutes. The chlorinated alkaline detergent hydrolyses and dissolves milk fats, proteins, and carbohydrates; removes protein deposits and prevents film build-up. Finally, the system is post-rinsed to remove the detergent residues. Often this step involves an acid rinse at about 38-49° C. (100-120° F.) that also helps remove scale, followed by a sanitizing step, or a single acid sanitizing rinse at about 21-38° C. (70-100° F.) using a combination acid sanitizer.
In Europe, the conventional cleaning process alternates between chlorinated alkaline detergent and acid detergent. According to these processes, one type of detergent is used for the morning cleaning, while the other type of detergent is used for the evening cleaning. These detergents are often combination cleaner-sanitizers. In the typical cleaning process, the system is pre-rinsed with ambient temperature or warm water, and then washed with hot water at about 60-80° C. using the acid or chlorinated alkaline detergent. The systems is then post-rinsed with ambient temperature water.
Chlorinated cleaning detergents are effective for cleaning CIP systems. However, the use of chlorinated alkaline detergents has several drawbacks, including corrosion and degradation of polymeric gaskets, hoses, and appliances in the milk handling equipment, as well as environmental concerns from discharge of the cleaning water from the system. Furthermore, chlorine concentrations are not easy to maintain in detersive solutions. The effectiveness of chlorine on protein soil removal diminishes as solution temperature and pH decreases. Also, chlorine can react with organic materials to form carcinogenic chlorocarbons, such as chloromethane, di- and trichloromethane, and various derivatives of chloroethane.
More recently, attempts have been made to increase the efficiency of cleaning CIP systems, as well as reduce the environmental impact of such processes, save energy, and reduce water consumption. However, conventional methods are not suitable to water re-use methods that are currently being explored. In these re-use methods, the water from the earlier cycle (i.e., the rinse water or wash water) is stored and reused for either the pre-rinse or wash water in the subsequent cleaning. However, acidic water from the post-rinse or the previous wash water partially neutralizes the alkalinity of the detergent used in the next cleaning cycle, or vice versa. This inhibits the effectiveness of the overall cleaning process and often results in the need for additional cleaning cycles thereby eliminating the benefits of recycling the water in the first place. Therefore, additional methods of improving the process of cleaning CIP systems have been sought.
WO 2005/090542 discloses a method of cleaning dairy equipment without the use of chlorine-containing alkaline detergents or a pre-rinse step. The method utilizes a cleaning solution containing at least one peroxide, which claims to take advantage of the lactoperoxidase enzymes and thiocyanate inherent in the dairy residue to be removed from the system. Lactoperoxidase and thiocyanate are disclosed in WO 2005/090542 as being a natural germicidals and anti-spoilants. The hydrogen peroxide in the disclosed cleaning solution activates the lactoperoxidase enzyme in the milk soil, which in turn kills the enzymes responsible for milk spoilage. A disadvantage to this system is that it is specific to dairy processing systems and would not work to clean other systems that do not have the lactoperoxidase enzymes or thiocyanate inherent in the soils to be removed from the dairy processing equipment. In addition, comparative testing of the disclosed peroxide cleaning solution indicates that there is only a 3-log reduction in the population of bacteria, which is not an acceptable level to be considered an antimicrobial or sanitizer in Europe or the United States.
Thus, there exists a real and substantial need in the art for a method of cleaning a clean-in-place system, which is not limited to dairy food or beverage processing plants, using a non-chlorine, acidic detergent composition capable of cleaning and descaling food preparation surfaces in a single cleaning cycle with a reduced volume pre-rinse step or entirely without a pre-rinse step, and further sanitizing under certain conditions. There is also a need for a method of recycling water from the cleaning process that avoids problems of traditional cleaning processes.